DC-transport Properties of QMG^® Current-Limiting Elements

Abstract

The V-I properties of YBCO bulk superconductor (QMG^®: YBa₂Cu₃O_7-x single-crystal containing Y₂BaCuO₅ particles) were measured using a single rectangular pulse current at 77 and 87K to obtain basic data for super-normal transition. Because of its high J_c property, QMG is a promising bulk material for resistive-type HTC-FCL application. I-shaped QMG rods having cross sections of 0.5×1.0mm were prepared to measure voltage due to pulse current. The plots of ln V vs ln I yielded a straight line with a gradient ranging from 5 to 7. By changing the amplitude and length of pulses, the time from the start of sending electricity till the occurrence of quench was obtained for various amplitudes of pulse current. In this experiment, it is considered that quenching did not occur in the whole rod but only in a small part of it.